О проекте Music Service

Relevant source files

The following files were used as context for generating this wiki page:

• README.md
• cmd/app/main.go
• internal/core/config/config.go
• internal/core/middleware/middleware.go
• migrations/001_init.up.sql
• docker-compose.yml
• internal/features/tracks/service/play.go

Music Subscription Service is a backend REST API developed in Go, designed to mimic the core functionalities of music streaming platforms like Spotify or Yandex Music. The system provides a comprehensive set of features for managing music catalogs, user subscriptions, playlists, and listening history.

The project follows a modular architecture where business logic is organized into "features" (Auth, Tracks, Playlists, etc.), supported by a core layer for infrastructure concerns like configuration, database connections, and middleware. It utilizes PostgreSQL for persistent storage, Redis for caching and rate-limiting, and JWT for secure authentication.

Sources: README.md:1-5, cmd/app/main.go:53-128, README.md:173-195

System Architecture

The application is built using a layered architecture with clear separation of concerns. The entry point is located in cmd/app/main.go, which handles dependency injection, configuration loading, and server initialization.

High-Level Components

• Transport Layer: Uses the chi router to handle HTTP requests.
• Service Layer: Contains business logic and enforces subscription-based limits.
• Repository Layer: Interacts with PostgreSQL using sqlx for data persistence.
• Core Layer: Provides shared utilities such as logging (zap), configuration, and middleware.

Database Schema

The system uses a relational schema in PostgreSQL to manage the music catalog and user-related data. The schema includes tables for users, artists, albums, tracks, and their relationships.

Entity Relationship Diagram

Table Definitions

Table	Description
users	Stores user credentials, roles (USER/ADMIN), and subscription_type.
tracks	Contains track metadata and file_url for audio streaming.
listening_history	Logs every track play with a timestamp for analytics.
playlist_tracks	A join table for the many-to-many relationship between playlists and tracks.

Sources: migrations/001_init.up.sql:1-96, README.md:149-158

Subscription & Limits Logic

A key feature of the service is the enforcement of limits based on the user's subscription type (FREE vs PREMIUM).

Limit Enforcement

The system uses Redis to track daily play counts for free users. If a user exceeds the FREE_DAILY_PLAY_LIMIT, the service rejects the play request.

Configuration Constants

Variable	Default Value	Description
FREE_DAILY_PLAY_LIMIT	10	Max tracks a FREE user can play per day.
FREE_PLAYLIST_LIMIT	3	Max playlists a FREE user can create.
JWT_ACCESS_TTL	15m	Lifetime of the access token.

Sources: internal/features/tracks/service/play.go:37-75, internal/core/config/config.go:42-43, README.md:49-50

Infrastructure and Deployment

The project is containerized using Docker and configured for automated deployment.

• Docker Compose: Manages three main services: app (Go backend), postgres, and redis.
• Healthchecks: The app service depends on postgres and redis being in a service_healthy state.
• CI/CD: Configured for Fly.io via GitLab CI/CD, using FLY_API_TOKEN for automated deployments upon merging to the main branch.

Sources: docker-compose.yml:5-50, README.md:200-225

Authentication Flow

Authentication is handled via JWT (JSON Web Tokens) with a rotation mechanism for refresh tokens.

1. Login: User provides credentials; the server returns an access_token and a refresh_token.
2. Authorization: The client includes the access_token in the Authorization: Bearer <token> header.
3. Middleware: The AuthMiddleware validates the token and injects Claims (UserID, Role, SubscriptionType) into the request context.
4. Token Refresh: When the access token expires, the client uses the refresh_token to obtain a new pair, which rotates the old refresh token in the database.

Sources: internal/core/middleware/middleware.go:115-148, internal/features/auth/service/refresh.go:15-68, cmd/app/main.go:121-140

The Music Service provides a robust foundation for a streaming platform, combining strict business rule enforcement with a scalable, containerized architecture.

Sources: README.md:1-5